Sunday 5 June 2011 19.05 EDT
First published on Sunday 5 June 2011 19.05 EDT

"In most interviews," writes Janet Malcolm in The Silent Woman, her 1993 book about Sylvia Plath, "both subject and interviewer give more than is necessary. They are always being seduced and distracted by the encounter's outward resemblance to an ordinary friendly meeting." Malcolm lives in an apartment in Manhattan, a very nice space, I remark, as she leads me through it and the 77-year-old smiles in such a way as to acknowledge an awkwardness: as a journalist, she has spent much of her career analysing the formal interview for hidden content, bad faith, above all flattery of a kind intended to encourage in the subject a false sense of security. "Thank you," she says stiffly. "Maybe you can write about that."

Malcolm has been called an academic, a biographer, an essayist; I once heard an Oxford professor dismiss her work as "gossip", which is to say she always gets the story. Occasionally, she becomes it. Twenty years after it was first published, The Journalist and the Murderer, her most famous book, about the lawsuit brought by a convicted murderer against the journalist who won his trust and then, as he saw it, betrayed him, is still causing outrage: last month, Joe McGinniss, the journalist of the title, protested once again about Malcolm's treatment of him in a letter to the New York Times Book Review. She was sued by another subject, Jeffrey Masson, after publication of In The Freud Archives, a case which dragged on for 10 years and was eventually dismissed by a jury. Her books bring a gimlet-eyed clarity to often fraught and complicated subjects and are so lean, so seamless, so powerfully direct, they read as if they have been written in a single breath.

The latest conflict to have triggered Malcolm's interest is a murder trial that took place in New York a few years ago, in which Mazoltuv Borukhova, a 35-year-old from Uzbekistan, was convicted of hiring a hit man to assassinate her husband, Daniel, after he won custody of their four-year-old daughter. Iphigenia In Forest Hills (Forest Hills is the neighbourhood in Queens where the family lived, within a community of Bukharan Jews) is Malcolm's documentation of the trial. She interviews the main characters, goes behind the scenes in the courtroom and does the thing she does best, finds the "mythic underpinning" as she puts it, to the modern-day story. "It was as inevitable," she writes, "that Borukhova would revenge herself on Daniel for the loss of Michelle as that Clytemnestra would revenge herself on Agamemnon for the loss of Iphigenia." It is a fascinating case, the enigma of which, writes Malcolm, is this: "She couldn't have done it and she must have done it."

Characteristically, the writer declares her own biases upfront. As jury selection gets under way, prospective jurors are asked if the fact the defendant is an educated woman, a doctor, would influence their judgment. Malcolm writes: "if I had been on that panel, I would, in all honesty, have had to raise my hand."

The person raising her hand in this scenario is not the same person, quite, as the one who wrote her first long piece for the New Yorker in 1978. "The invented I of journalism" as Malcolm calls it, is not a stable entity. One of the things she realised early on in her writing career was that, she says, "this 'I' was a character, just like the other characters. It's a construct. And it's not the person who you are. There's a bit of you in it. But it's a creation. Somewhere I wrote, 'the distinction between the I of the writing and the I of your life is like Superman and Clark Kent.'"

Her super-power is a kind of x-ray vision, the power to see through people's pretensions. Masson, a psychotherapist who was made head of the Freud Archives in 1980 before falling out with the entire psychotherapeutic establishment, was hung by his own grandiose quotes, as the subject of Malcolm's book about the dispute, with some help from the writer (she described him as looking "a bit plump and spoiled" and went on to quote his foolish interactions with the maître d' at lunch). Malcolm's critique of her subjects is tempered by an equally stringent self-criticism, which, in the absence of much humour, can present now and then as piety. In The Journalist and the Murderer she calls herself out for the "self-satisfied tone" and "fundamental falseness" of her letters to Jeffrey MacDonald, the convicted murderer with whom she is trying to establish a rapport. She has written more generally about the cruelties of her trade, most famously in the opening line of that book, which caused outrage at the time but is now more or less taken for granted: "Every journalist who is not too stupid or too full of himself to notice what is going on knows that what he does is morally indefensible." That she does not exempt herself from this judgment is, in itself, a subtle bid for at least partial exemption, as the naming of one's faults tends to be.

Malcolm says that when she wrote that opening line, she thought she was stating the obvious. "It was such a surprise that journalists got so mad at me. It seemed so completely like a truism, which it now is. So I was unprepared. I was living in this sort of cocoon that people at the New Yorker seemed to live in then. I didn't think anyone would be upset by it."

They were upset because you broke the code?

"Yeah," she says. (There was also, I imagine, some resentment at the fancy end of journalism pronouncing with such lofty assurance on the shortcomings of all.)

Malcolm's position as an outsider is a structural necessity in her work that requires for its drama the establishment, early on, of transgressions and self-deceits in the thing she is writing about. In The Journalist and the Murderer it is the press; in the Plath book, it is biography – she likens biographers to "the professional burglar, breaking into a house, rifling through certain drawers that he has good reason to think contain the jewellery and money, and triumphantly bearing his loot away." Readers aren't let off the hook either: "bovine equanimity" is how she describes the state in which the "lay reader" consumes a biography.

She has written sparingly of the details of her own life. She grew up in New York, one of two daughters of Czech immigrants. Her father was a psychiatrist, her mother had been a lawyer in Czechoslovakia but did not resume practice in the US. They were a loud family, a family of interrupters she has said and I wonder if that has anything to do with her ability to get swiftly to the point.

"Probably, yes. Maybe it's just my own character, too; I'm impatient and bore easily, and so I assume others will be bored and I don't want to be boring."

As a child she recalls not understanding English and then suddenly understanding it and being relieved. No sense of outsidership remains. "It was more that I wanted to assimilate. I wanted to be American. And didn't want to be foreign. That was the wish." She reads Czech, badly; it was the only language her father wrote in, mainly technical papers. "That was the sad part. He never became a writer in English."

After college, she started writing for the New Yorker. "I did a column called 'Gifts', that was at Christmas time, and I did a column during the year called 'About the House', about shopping for nice things. I feel fortunate in having had that apprenticeship; learning to describe things in an off-stage way. Nobody paid very much attention to me. It was a wonderful education."

It was a very traditionally girly beat.

"Yes, you're right. I guess I was so part of that culture that I didn't even think of it as a girls' ghetto. But it was. Women wrote about those things. There were no men writing those shopping columns. And I also reviewed children's books – that, too, women did. I had a small child then, so it was great." Her first husband, Donald Malcolm, was a writer; her second, Gardner Botsford, was her editor at the New Yorker. The breakthrough in her career came in the late 70s when she went to Philadelphia to write a long story about family therapy, just then taking off, the idea for which had come from talking to her father. She took the trip partly in an effort to distract herself from quitting smoking. "I needed to do something. I reported it for a long time. And then I gradually learned to write it up, without cigarettes."

The first-person approach came naturally to her she says, influenced by the work of Joseph Mitchell, her colleague at the New Yorker. Botsford, who was 17 years her senior, was "a big cutter" and "a strict editor. I was very lucky". He died in 2004. Has she been tempted, in the Joan Didion/Joyce Carol Oates fashion, to write about the experience of widowhood? She gives me a glittering look.

"Absolutely not," she says.

During the course of researching Iphigenia in Forest Hills, Malcolm did something she has never as a journalist done before: she interfered with the story. The man responsible for awarding custody of the couple's child to Borukhova's husband, despite the woman's accusations he'd abused both her and the child, revealed himself in an interview with Malcolm to believe that 9/11 was a conspiracy, that the world was run by a secret "communist-like system," and to hold a range of other opinions that would, surely, reduce his credibility as a witness. She passed on her notes to the defence attorney, who asked the judge for permission to re-question the man, after evidence had come to light "concerning his mental health". The judge denied the request.

It is often overlooked how good a reporter Malcolm is, fearless in her questioning, ruthless in her pursuit of every last witness. The Journalist and the Murderer, an account of the lawsuit brought by Jeffrey MacDonald, a convicted murderer, against McGinniss, the writer who charmed him into co-operating with his book Fatal Vision, and then condemned him in the copy, is a lesson in not courting your subject too much. This was underlined for Malcolm in the lawsuit brought against her by Masson, after publication of In The Freud Archives. Masson comes across in the book as a bit silly rather than immoral, a reminder that wounding someone's vanity is a greater provocation than ostensibly graver injuries.

The experience of the lawsuit changed Malcolm's approach. "I came to realise – and Joe McGinniss was the awful example of this – that you don't have to be as friendly to the people you write about . . . I'm a lot more neutral. I don't go out of my way to be friendly, because it's completely unnecessary. People tell you what they are going to tell you no matter what."

It's tough, I suggest, because even in professional settings people want to be liked.

"It's hard to change. But I think you have to, especially if you know you're going to write coldly about them."

Was she surprised by the things Masson got upset about? (His legal action eventually centred on five quotes, among them: "[Analysts] will want me back, they will say that Masson is a great scholar, a major analyst – after Freud, he's the greatest analyst who ever lived.")

"Yes. He was telling it to me, so why was he so upset? It was such a complicated mess. And it's done."

In her professional encounters Malcolm benefits, perhaps, from the fact she is small and deceptively slight. "I am unthreatening in ordinary life," she says. "But when you write about someone – that's the threat. That's the distinction. It's very easy to be unthreatening and nice. But then you have to take that harder step – that's when the aggression and heartlessness comes to the fore: in the writing."

It doesn't come easily, she says. "I'm a very laboured writer. I hammer it out sentence by sentence and it takes a long time. That's what the work is, right? To make the reader think it is not hard to do." She works mainly in the morning; the first hour is the most crucial, when her best work gets done. "I'll put in the rest of the time, but whatever gets done will get done in that hour. If I write a page a day I feel very good about it. And there are days when I write minus a page. See that what I did the day before was wrong and lose that. I try to stop at a point where I can – it's already moving towards something. Something unfinished, rather than having to start something new."

She does not have a sense of ultimate destination. "I vaguely know, but I don't want to know too much, because then it's like painting by numbers, to have it all mapped out. And the hardest part is beginning. I have many, many false starts. If it's not the right start, then it doesn't go anywhere. It stops. And you have to find some start to set it going in the right direction."

She looks at me rather accusingly. "I don't analyse what I do; I do it."

Hang on, yes she does – she analyses her role as a journalist.

"As an observer, I'm analysing my reactions I guess and my thinking; but about the process of writing . . ." She says: "I am not very talented at talking about what I do as a writer."

Of all the people Malcolm has interviewed, one of the few who wouldn't play the game was Jacqueline Rose, the academic and author of a book about Sylvia Plath, who features in The Silent Woman and of whom Malcolm is as admiring as of anyone. "Rose never," she writes, "or almost never – forgot, or let me forget, that we were not two women having a friendly conversation over a cup of tea and a box of biscuits but participants in a special, artificial exercise of subtle influence and counterinfluence, with an implicit antagonistic tendency."

When I turned up at her apartment, I had brought Malcolm iced coffee, which she turned down. "I'm a tea drinker," she said and I ended up drinking both coffees. I feel bad, I say, at the end of the interview, for bringing things I've wound up consuming myself. Malcolm smiled. "Is it a metaphor for something?" she said.